Nonbank financial intermediaries (NBFIs) have grown significantly relative to banks. We argue that this growth reflects a transformation of the activities and risks of banks and NBFIs, driven at least in part by changes in bank regulation. We document through new regulatory data, case studies, and empirical analyses that banks remain special as providers of both routine and emergency liquidity to NBFIs and that the sectors have become increasingly interdependent. We discuss some potential regulatory responses, including considering the two sectors holistically and exploring new ways to internalize the costs of systemic risk arising from bank-NBFI interconnectedness.

We present a model of equilibrium allocation of capital for arbitrage. If asset prices may fall low enough, it is profitable to carry liquid capital to acquire assets in such states. Set against this, keeping capital in liquid form entails costs in terms of foregone profitable investments. This trade-off generates occasional fire sales and limited arbitrage capital as robust phenomena. With learning-by-doing effects, arbitrage capital moves in to acquire assets only if fire sales are steep. However, once arbitrage capital finds it profitable to acquire assets, it requires similar returns elsewhere, inducing contagious fire-sale prices even for unrelated assets.